One line of scientific enquiry is how the biodiversity and habitat characteristics differ across the partitions, and more importantly, if the same species are present, are they genetically isolated or are there mechanism for gene flow?
The bigger picture is do with scale. If we can examine populations between these areas separated only a seamount, and then between the Mariana and the neighbouring trenches such as Izu-Bonin and Japan, to trench clusters in other Pacific regions, (e.g. San Cristobal and Santa Cruz trenches, or Tonga and Kermadec trenches), to trenches in other oceans (such as the Java trench in the Indian Ocean, or South Sandwich in the Southern ocean), then we can ask questions about genetic connectivity and speciation on multiple scales. We can start to unravel what is a global function of depth (being ‘hadal’) and what is a function of local environmental conditions.